import type { SubagentState } from "../../shared/types.ts";

const MAX_CLAIMED_PREDECESSOR_SESSIONS = 8;

type ResultDeliveryState = Pick<SubagentState, "currentSessionId" | "completionOwnerId">;

export interface ResultDeliveryOwnership {
	owns(sessionId: string, completionOwnerId: unknown): boolean;
	claimedSessionIds(): readonly string[];
	claimPredecessor(previousSessionFile: string | undefined, previousRuntimeSessionId: string | null): boolean;
	clear(): void;
}

export function createResultDeliveryOwnership(state: ResultDeliveryState): ResultDeliveryOwnership {
	const claimed = new Map<string, string>();

	const currentOwner = (): string | undefined => typeof state.completionOwnerId === "string" && state.completionOwnerId
		? state.completionOwnerId
		: undefined;

	return {
		owns(sessionId, completionOwnerId) {
			const owner = currentOwner();
			if (!owner || completionOwnerId !== owner) return false;
			return sessionId === state.currentSessionId || claimed.get(sessionId) === owner;
		},
		claimedSessionIds() {
			const owner = currentOwner();
			if (!owner) return [];
			return [...claimed].flatMap(([sessionId, claimedOwner]) => claimedOwner === owner ? [sessionId] : []);
		},
		claimPredecessor(previousSessionFile, previousRuntimeSessionId) {
			const owner = currentOwner();
			if (!owner || !previousSessionFile || !previousRuntimeSessionId) return false;
			if (previousSessionFile !== previousRuntimeSessionId || state.currentSessionId !== previousRuntimeSessionId) return false;
			claimed.delete(previousRuntimeSessionId);
			claimed.set(previousRuntimeSessionId, owner);
			while (claimed.size > MAX_CLAIMED_PREDECESSOR_SESSIONS) claimed.delete(claimed.keys().next().value!);
			return true;
		},
		clear() {
			claimed.clear();
		},
	};
}